SAN FRANCISCO -- Wall Street is chirping about Twitter, which seems to be defying gravity. Shares are setting record highs in midday trading Tuesday, soaring above $50, despite mixed reviews from analysts. The cause of investor enthusiasm: Twitter's move into more targeted advertising that has been a boon for Facebook. Analysts say these ads are potentially very lucrative for social networks under pressure from investors to wring more revenue from users. Twitter said last week that it was rolling out retargeting ads for its more than 230 million active users.

SAN FRANCISCO - Social networks have found a promising new source of advertising revenue: targeting users with ads for products they browsed online. The latest form of advertising, called "retargeting," is expected to not only get more pervasive but intensify worries over privacy. Tania Mulry, an entrepreneur from Santa Clarita, said she and other people are noticing and talking about the flood of retargeting ads. One of Mulry's students in a mobile app design class at USC was unnerved that a swimsuit she browsed on Nordstrom.com showed up as an ad on her Facebook page.

Keaton Row has added a new twist to online shopping. The website, created by Harvard Business School graduates Cheryl Han and Elenor Mak, pairs shoppers with fashion advisors from all over the country, based on a personal style Q&A given to each new member who signs onto the site. Think online dating but with a refreshed and personalized wardrobe, not a first date, as the goal. "What we realized is that people want a back-to-basics, personal touch when shopping online," Han says.

SAN FRANCISCO -- Twitter may still be a small player in the digital advertising world, but its advertising platform has more promise than that of Facebook and could justify the company's potential market value, which has risen by several billion dollars ahead of its initial public offering on Thursday. That's according to a new national survey from Frank N. Magid Associates, which says consumers respond more positively to ads on Twitter than they do to ads on Facebook - in large part because the ads blend so smoothly into the service.

What do you do when you have millions and millions of Twitter followers? One option is to fund your very own social network. Teenage pop star Justin Bieber, the second-most popular person on Twitter with 46.5 million followers, has reportedly led a $1.1-million round of funding for RockLive, a San Francisco tech company that plans to launch a new social network this week. The social network will be called Shots of Me and will focus on teenagers, according to Fortune . WATCH: Unboxing the Google Nexus 5 smartphone [Video chat]

MESQUITA, Brazil - As Dilma Rousseff neared the end of her successful 2010 campaign to become Brazil's president, Jeferson Monteiro set up a parody Twitter account and began having fun at her expense. When Rousseff took office and abandoned her own account on the microblogging service, Monteiro began sending tweets as the president, adopting the manic and self-obsessed vernacular common to the teenagers dominating the social media networks. He gently lampooned a president often seen as serious and tough.

SAN FRANCISCO - Parents take note: Your teens can now post status updates and photos on Facebook for anyone to see. The giant social network on Wednesday lifted restrictions on kids ages 13 to 17 that kept them from sharing information with people they do not know. Until now, teens' posts on Facebook could be viewed only by friends and the friends of their friends. The move presents a tough new challenge to parents trying to keep their kids safe on social media. Facebook said it was bringing its privacy policy in line with competitors' by giving teens the freedom to decide whether they want to express themselves among a close circle of friends or with a bullhorn.

With the "Breaking Bad" series finale coming this weekend, it's certain that a flurry of spoilers are going to be plastered across Facebook and Twitter. But there is a way to avoid seeing them without having to spend Sunday night under a rock. A free iPhone and iPad app that launched this week called Spoiler Shield claims to be able to block spoilers from "Breaking Bad" while still giving users access to other content on their Facebook and Twitter feeds. PHOTOS: Top 11 hidden, cool features in Apple's iOS 7 Besides "Breaking Bad," Spoiler Shield can also block spoilers from about 30 other TV shows as well as NFL and Major League Baseball results.

TEHRAN -- One day Facebook is a handy way for Iranian government ministers to confer with the people. The next day it can be denounced as "a Zionist tool. " As with its on-again, off-again claim to want better relations with the West, Iran's recent flip-flops on social media reflect infighting within Tehran's religious and elected leaderships, analysts said Tuesday. Iranians were jubilant on Monday when the usual blockages and filters on social media sites like Twitter and Facebook fell by the wayside.

Fernando Anglero is a fixture among the street people who live in downtown L.A.'s Arts district, known for his off-color, funny signs that one local loft-dweller says bring "fun energy" to the neighborhood. But the homeless man residents know only as Fernando stands out for another reason -- he's marketing himself as a street comic using social media. To promote his "cardboard comedy," Anglero has created a website with help from Arts district residents. He also has a Facebook page and a personal hashtag, #fernandolove, to make it easier to find him on Instagram and Twitter.